U.S. patent application number 11/170061 was filed with the patent office on 2006-02-23 for slurry, chemical mechanical polishing method using the slurry, and method of forming a surface of a capacitor using the slurry.
Invention is credited to Chang-Ki Hong, Sung-Jun Kim, Jae-Dong Lee, Haruki Nojo, Kenichi Orui, Seong-Kyu Yun.
Application Number | 20060037942 11/170061 |
Document ID | / |
Family ID | 36772636 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060037942 |
Kind Code |
A1 |
Yun; Seong-Kyu ; et
al. |
February 23, 2006 |
Slurry, chemical mechanical polishing method using the slurry, and
method of forming a surface of a capacitor using the slurry
Abstract
A slurry, chemical mechanical polishing (CMP) method using the
slurry, and method of forming a surface of a capacitor using the
slurry. The slurry may include an abrasive, an oxidizer, and at
least one pH controller to control a pH of the slurry.
Inventors: |
Yun; Seong-Kyu; (Seoul,
KR) ; Orui; Kenichi; (Ausugi-shi, JP) ; Hong;
Chang-Ki; (Seongnam-si, KR) ; Lee; Jae-Dong;
(Suwon-si, KR) ; Kim; Sung-Jun; (Suwon-si, KR)
; Nojo; Haruki; (Kouza-gun, JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 8910
RESTON
VA
20195
US
|
Family ID: |
36772636 |
Appl. No.: |
11/170061 |
Filed: |
June 30, 2005 |
Current U.S.
Class: |
216/88 ; 216/89;
252/79.1; 252/79.5; 257/E21.244; 257/E21.304; 438/692 |
Current CPC
Class: |
C09G 1/02 20130101; C09K
3/1463 20130101; H01L 21/3212 20130101; C03C 2218/328 20130101;
H01L 21/31053 20130101; C03C 19/00 20130101 |
Class at
Publication: |
216/088 ;
216/089; 252/079.1; 252/079.5; 438/692 |
International
Class: |
C09K 13/00 20060101
C09K013/00; C03C 15/00 20060101 C03C015/00; H01L 21/302 20060101
H01L021/302 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 17, 2004 |
KR |
10-2004-0064648 |
Claims
1. A slurry for a chemical mechanical polishing (CMP) method for a
film including ruthenium, comprising: an abrasive; an oxidizer; and
at least one pH controller to control a pH of the slurry.
2. The slurry of claim 1, wherein the film includes at least one of
a ruthenium oxide and a ruthenium alloy.
3. The slurry of claim 1, wherein the pH is in a range from 2 to
8.
4. The slurry of claim 3, wherein the pH is in a range from 3.5 to
4.5.
5. The slurry of claim 4, wherein the pH is about 4.
6. The slurry of claim 1, wherein the at least one pH controller
includes an amine.
7. The slurry of claim 6, wherein the at least one pH controller
includes at least one material selected from the group consisting
of BHMT (Bis-(HexamMethylene)Triamine), TMAH (TetraMethyl Ammonium
Hydroxide), TMA (TetraMethylAmine), TEA (TetraEthylAmine), HA
(Hydroxylamine), PEA (PolyEthyleneAmine), CH (Choline Hydroxide)
and salts thereof.
8. The slurry of claim 7, wherein the at least one pH controller
includes TMA.
9. The slurry of claim 8, wherein the slurry includes an amount of
TMA such that the pH of the slurry is about 4.
10. The slurry of claim 7, wherein the at least one pH controller
includes TMAH.
11. The slurry of claim 10, wherein the slurry includes an amount
of TMAH such that the pH of the slurry is about 4.
12. The slurry of claim 11, wherein the abrasive is colloidal
silica and the oxidizer is periodic acid.
13. The slurry of claim 12, wherein a content of the periodic acid
is in a range from 0.1 to 5 weight % of a total weight of the
slurry.
14. The slurry of claim 13, wherein a content of the colloidal
silica is in a range from 0.01 to 30 weight % of a total weight of
the slurry.
15. The slurry of claim 14, wherein a content of the colloidal
silica is in a range from 0.1 to 10 weight % of a total weight of
the slurry.
16. The slurry of claim 15, wherein a content of the colloidal
silica is in a range from 0.5 to 3 weight % of a total weight of
the slurry.
17. The slurry of claim 16, wherein a content of the colloidal
silica is 0.5 weight % of a total weight of the slurry and a
content of the periodic acid is 0.5 weight % of a total weight of
the slurry.
18. The slurry of claim 16, wherein a content of the colloidal
silica is 3 weight % of a total weight of the slurry and a content
of the periodic acid is 0.5 weight % of a total weight of the
slurry.
19. The slurry of claim 1, wherein the at least one pH controller
includes potassium hydroxide.
20. The slurry of claim 1, wherein the abrasive includes at least
one material selected from the group consisting of ceria, silica,
colloidal silica, fumed silica, alumina, titania, angania,
zirconia, germania, or mixtures thereof.
21. The slurry of claim 20, wherein a content of the abrasive is in
a range from 0.01 to 30 weight % of a total weight of the
slurry.
22. The slurry of claim 21, wherein the content of the abrasive is
in a range from 0.1 to 10 weight % of a total weight of the
slurry.
23. The slurry of claim 1, wherein the oxidizer includes periodic
acid.
24. The slurry of claim 23, wherein a content of the periodic acid
is in a range from 0.1 to 5 weight % of a total weight of the
slurry.
25. The slurry of claim 24, wherein the content of the periodic
acid is in a range from 0.5 to 1.5 weight % of a total weight of
the slurry.
26. A chemical mechanical polishing (CMP) method for a ruthenium
film formed on a semiconductor substrate, the method comprising:
preparing a slurry including an abrasive, an oxidizer, and at least
one pH controller to control a pH of the slurry; and performing
chemical mechanical polishing (CMP) of the ruthenium film using the
slurry.
27. The method of claim 26, wherein a removal rate selectivity of
the slurry is greater than or equal to 5:1.
28. The method of claim 27, wherein a removal rate selectivity of
the slurry is greater than or equal to 20:1.
29. The method of claim 28, wherein a removal rate selectivity of
the slurry is greater than or equal to 50:1.
30. The method of claim 26, wherein the film includes at least one
of a ruthenium oxide and a ruthenium alloy.
31. The method of claim 26, wherein the pH is in a range from 2 to
8.
32. The method of claim 31, wherein the pH is in a range from 3.5
to 4.5.
33. The method of claim 32, wherein the pH is about 4.
34. The method of claim 26, wherein the at least one pH controller
includes an amine.
35. The method of claim 34, wherein the at least one pH controller
includes at least one material selected from the group consisting
of BHMT (Bis-(HexamMethylene)Triamine), TMAH (TetraMethyl Ammonium
Hydroxide), TMA (TetraMethylAmine), TEA (TetraEthylAmine), HA
(Hydroxylamine), PEA (PolyEthyleneAmine), CH (Choline Hydroxide)
and salts thereof.
36. The method of claim 35, wherein the at least one pH controller
includes TMA.
37. The method of claim 36, wherein the slurry includes an amount
of TMA such that the pH of the slurry is about 4.
38. The method of claim 35, wherein the at least one pH controller
includes TMAH.
39. The method of claim 38, wherein the slurry includes an amount
of TMAH such that the pH of the slurry is about 4.
40. The method of claim 39, wherein the abrasive is colloidal
silica and the oxidizer is periodic acid.
41. The method of claim 40, wherein a content of the periodic acid
is in a range from 0.1 to 5 weight % of a total weight of the
slurry.
42. The method of claim 41, wherein a content of the colloidal
silica is in a range from 0.01 to 30 weight % of a total weight of
the slurry.
43. The method of claim 42, wherein a content of the colloidal
silica is in a range from 0.1 to 10 weight % of a total weight of
the slurry.
44. The method of claim 43, wherein a content of the colloidal
silica is in a range from 0.5 to 3 weight % of a total weight of
the slurry.
45. The method of claim 44, wherein a content of the colloidal
silica is 0.5 weight % of a total weight of the slurry and a
content of the periodic acid is 0.5 weight % of a total weight of
the slurry.
46. The method of claim 44, wherein a content of the colloidal
silica is 3 weight % of a total weight of the slurry and a content
of the periodic acid is 0.5 weight % of a total weight of the
slurry.
47. The method of claim 26, wherein the at least one pH controller
includes potassium hydroxide.
48. The method of claim 26, wherein the abrasive includes at least
one material selected from the group consisting of ceria, silica,
colloidal silica, fumed silica, alumina, titania, angania,
zirconia, germania, or mixtures thereof.
49. The method of claim 48, wherein a content of the abrasive is in
a range from 0.01 to 30 weight % of a total weight of the
slurry.
50. The method of claim 49, wherein the content of the abrasive is
in a range from 0.1 to 10 weight % of a total weight of the
slurry.
51. The method of claim 26, wherein the oxidizer includes periodic
acid.
52. The method of claim 51, wherein a content of the periodic acid
is in a range from 0.1 to 5 weight % of a total weight of the
slurry.
53. The method of claim 52, wherein the content of the periodic
acid is in a range from 0.5 to 1.5 weight % of a total weight of
the slurry.
54. A method for forming a surface for a capacitor comprising:
forming an etch stop layer on a semiconductor substrate; forming a
mold oxide layer on the etch stop layer; patterning the mold oxide
layer to define a region for the capacitor; forming a layer
including ruthenium on the patterned mold oxide layer; forming a
dielectric layer on the layer including ruthenium; and polishing
the layer including ruthenium and the dielectric layer using a
slurry including an abrasive, an oxidizer, and at least one pH
controller to control a pH of the slurry.
55. The method of claim 54, wherein patterning the mold oxide layer
includes using at least one of a hard mask and a photoresist.
56. The method of claim 54, wherein the mold oxide layer is one of
PE-TEOS, PE-OX, HDP, USG, and a BPSG layer.
57. The method of claim 54, wherein the layer including ruthenium
is deposited by sputtering, by chemical vapor deposition (CVD), or
by ALD.
58. The method of claim 54, wherein the dielectric layer includes
Ta, Hf, Al, Ti, Sb--Ti (STO), BST oxides or combinations
thereof.
59. The method of claim 54, wherein a removal rate selectivity of
the slurry is greater than or equal to 5:1.
60. The method of claim 59, wherein a removal rate selectivity of
the slurry is greater than or equal to 20:1.
61. The method of claim 60, wherein a removal rate selectivity of
the slurry is greater than or equal to 50:1.
62. The method of claim 54, further comprising: forming a spacer
prior to forming the layer including ruthenium.
63. The method of claim 62, wherein the spacer includes Ta, Hf, Al,
Ti, Sb--Ti (STO), BST oxides or combinations thereof.
64. The method of claim 54, wherein the capacitor is one of a
stacked, concave, or OCS capacitor.
65. The method of claim 54, wherein the layer including ruthenium
includes at least one of a ruthenium oxide and a ruthenium
alloy.
66. The method of claim 54, wherein the pH is in a range from 2 to
8.
67. The method of claim 66, wherein the pH is in a range from 3.5
to 4.5.
68. The method of claim 67, wherein the pH is about 4.
69. The method of claim 56, wherein the at least one pH controller
includes an amine.
70. The method of claim 69, wherein the at least one pH controller
includes at least one material selected from the group consisting
of BHMT (Bis-(HexamMethylene)Triamine), TMAH (TetraMethyl Ammonium
Hydroxide), TMA (TetraMethylAmine), TEA (TetraEthylAmine), HA
(Hydroxylamine), PEA (PolyEthyleneAmine), CH (Choline Hydroxide)
and salts thereof.
71. The method of claim 70, wherein the at least one pH controller
includes TMA.
72. The method of claim 71, wherein the slurry includes an amount
of TMA such that the pH of the slurry is about 4.
73. The method of claim 70, wherein the at least one pH controller
includes TMAH.
74. The method of claim 73, wherein the slurry includes an amount
of TMAH such that the pH of the slurry is about 4.
75. The method of claim 74, wherein the abrasive is colloidal
silica and the oxidizer is periodic acid.
76. The method of claim 75, wherein a content of the periodic acid
is in a range from 0.1 to 5 weight % of a total weight of the
slurry.
77. The method of claim 76, wherein a content of the colloidal
silica is in a range from 0.01 to 30 weight % of a total weight of
the slurry.
78. The method of claim 77, wherein a content of the colloidal
silica is in a range from 0.1 to 10 weight % of a total weight of
the slurry.
79. The method of claim 78, wherein a content of the colloidal
silica is in a range from 0.5 to 3 weight % of a total weight of
the slurry.
80. The method of claim 79, wherein a content of the colloidal
silica is 0.5 weight % of a total weight of the slurry and a
content of the periodic acid is 0.5 weight % of a total weight of
the slurry.
81. The method of claim 80, wherein a content of the colloidal
silica is 3 weight % of a total weight of the slurry and a content
of the periodic acid is 0.5 weight % of a total weight of the
slurry.
82. The method of claim 54, wherein the at least one pH controller
includes potassium hydroxide.
83. The method of claim 54, wherein the abrasive includes at least
one material selected from the group consisting of ceria, silica,
colloidal silica, fumed silica, alumina, titania, angania,
zirconia, germania, or mixtures thereof.
84. The method of claim 83, wherein a content of the abrasive is in
a range from 0.01 to 30 weight % of a total weight of the
slurry.
85. The method of claim 84, wherein the content of the abrasive is
in a range from 0.1 to 10 weight % of a total weight of the
slurry.
86. The method of claim 54, wherein the oxidizer includes periodic
acid.
87. The method of claim 86, wherein a content of the periodic acid
is in a range from 0.1 to 5 weight % of a total weight of the
slurry.
88. The method of claim 87, wherein the content of the periodic
acid is in a range from 0.5 to 1.5 weight % of a total weight of
the slurry.
Description
PRIORITY STATEMENT
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119(a) of Korean Patent Application No. 2004-0064648 filed on Aug.
17, 2004, the contents of which are hereby incorporated by
reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] Ruthenium, including ruthenium alloys, such as ruthenium
dioxide, may be used as a bottom electrode material of a capacitor
for a semiconductor device. A ruthenium alloy may be defined as any
composition where ruthenium is the main component. Ruthenium
alloys, such as ruthenium dioxide, may have a lower surface
resistance because of their conductivity, contrary to other
materials, such as titanium oxide, tungsten oxide or tantalum
oxide.
[0003] Conventionally, a ruthenium film may be deposited using a
sputtering method or a CVD method, and afterward, some portion of
the ruthenium film may be removed to form a bottom electrode by
etching the ruthenium film. However, it may be difficult to etch a
ruthenium film by conventional wet etch processes, using
conventional etchants, including aqua-regia or a "piranha" etchant.
A "piranha" etchant is a semiconductor industry-accepted term for a
conventional wet chemical solution containing sulfuric acid and
hydrogen peroxide, often used to clean substrates of organic
contamination.
[0004] Another conventional solution for wet etching a ruthenium
film is a solution including ceric ammonium nitrate,
(NH.sub.4).sub.2Ce(NO.sub.3).sub.6, which can be used as a wet
etchant or a chemical mechanical polish (CMP) slurry. However,
ceric ammonium nitrate has several drawbacks. First, it may be
difficult to control the removal rate of ruthenium because of ceric
ammonium nitrate's high speed. Second, ceric ammonium nitrate may
cause damage to processing machinery due to its high acidity (pH of
about 1). Third, it may be difficult to control the pH of the wet
etch solution because a precipitate is formed from the combination
of cerium ions (Ce.sup.4+) and hydroxyl anions (OH.sup.-) and
therefore it may also be difficult to control the selectivity
between the ruthenium film(s) and other films.
[0005] Due to the above-mentioned problems with wet etching a
ruthenium film, ruthenium films have also been etched using dry
etch processes. However, dry etching ruthenium films may also have
problems, including the formation of sharp cusps on a top surface
of the ruthenium bottom electrode after node separation, recessing
of the ruthenium bottom electrode and/or a loss of mold oxide, and
a resultant loss of capacitance.
SUMMARY OF THE INVENTION
[0006] Example embodiments of the present invention are directed to
a slurry for a chemical mechanical polishing (CMP) method for
polishing a metal film, such as an ruthenium film, which provides a
high removal rate selectivity of metal film to other films, a
polishing method, for example, a CMP method, using the slurry, and
a method of forming a surface for a capacitor using the polishing
method.
[0007] Example embodiments of the present invention are directed to
a slurry, a polishing method, and a method of forming a surface for
a capacitor with improved removal rate selectivity and/or better pH
control.
[0008] Example embodiments of the present invention are directed to
slurry for a chemical mechanical polishing (CMP) method for a film
including ruthenium, the slurry including an abrasive, an oxidizer,
and at least one pH controller to control a pH of the slurry.
[0009] Example embodiments of the present invention are also
directed to a chemical mechanical polishing (CMP) method for a
ruthenium film formed on a semiconductor substrate, the method
including preparing a slurry including an abrasive, an oxidizer,
and at least one pH controller to control a pH of the slurry and
performing chemical mechanical polishing (CMP) of the ruthenium
film using the slurry.
[0010] Example embodiments of the present invention are also
directed to a method for forming a surface for a capacitor
including forming an etch stop layer on a semiconductor substrate,
forming a mold oxide layer on the etch stop layer, patterning the
mold oxide layer to define a region for the capacitor, forming a
layer including ruthenium on the patterned mold oxide layer,
forming a dielectric layer on the layer including ruthenium, and
polishing the layer including ruthenium and the dielectric layer
using a slurry including an abrasive, an oxidizer, and at least one
pH controller to control a pH of the slurry.
[0011] In example embodiments of the present invention, the
capacitor is one of a stacked, concave, or OCS capacitor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will become more fully understood from
the detailed description given below and the accompanying drawings,
which are given for purposes of illustration only, and thus do not
limit the invention.
[0013] FIGS. 1-7 illustrate a method of forming a stacked capacitor
using ruthenium or ruthenium alloy as a bottom electrode in
accordance with example embodiments of the present invention.
[0014] FIGS. 8-17 illustrate a method of forming a concave
capacitor using ruthenium or ruthenium alloy as a bottom electrode
in accordance with example embodiments of the present
invention.
[0015] FIG. 18 illustrate a One Cylinder Stack (OCS) structure
capacitor in accordance with example embodiments of the present
invention.
[0016] It should be noted that these Figures are intended to
illustrate the general characteristics of methods and devices of
example embodiments of this invention, for the purpose of the
description of such example embodiments herein. These drawings are
not, however, to scale and may not precisely reflect the
characteristics of any given embodiment, and should not be
interpreted as defining or limiting the range of values or
properties of example embodiments within the scope of this
invention.
[0017] In particular, the relative thicknesses and positioning of
layers or regions may be reduced or exaggerated for clarity.
Further, a layer is considered as being formed "on" another layer
or a substrate when formed either directly on the referenced layer
or the substrate or formed on other layers or patterns overlaying
the referenced layer.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE PRESENT
INVENTION
[0018] In an example embodiment of the invention, a slurry for use
in chemical mechanical polishing (CMP) may include an abrasive, an
oxidizer, and/or a pH controller.
[0019] In an example embodiment, the abrasive may be ceria, silica
(in any form, for example, colloidal or fumed silica), alumina,
titania, angania, zirconia, germania or mixtures thereof.
[0020] In an example embodiment, the oxidizer may be or include
periodic acid (H.sub.5IO.sub.6).
[0021] In an example embodiment, the pH controller may be or
include an amine compound, for example, BHMT
(Bis-(HexamMethylene)Triamine), TMAH (TetraMethyl Ammonium
Hydroxide), TMA (TetraMethylAmine), TEA (TetraEthylAmine), HA
(Hydroxylamine), PEA (PolyEthyleneAmine), CH (Choline Hydroxide)
and/or choline salt. In other example embodiments, the pH
controller may be potassium hydroxide.
[0022] In an example embodiment, the abrasive, for example,
colloidal silica, may be from 0.01 to 30 (inclusive, as are all
ranges disclosed and claimed herein) weight % of the CMP slurry,
and more particularly, from 0.1 to 10 weight %, and more
particularly, from 0.5 to 3.0 weight %.
[0023] In an example embodiment, the oxidizer, for example,
periodic acid, may be from 0.1 to 5 weight % of the CMP slurry. In
an example embodiment, a content of the oxidizer, for example,
periodic acid, may be in a range from 2.5 to 5.0 weight % of a
total weight of the slurry. In an example embodiment, a content of
the oxidizer, for example, periodic acid, may be in a range from
0.1 to 2.0 weight % of a total weight of the slurry. In an example
embodiment, a content of the oxidizer, for example, periodic acid,
may be in a range from 0.1 to 1.0 weight % of a total weight of the
slurry. In an example embodiment, a content of the oxidizer, for
example, periodic acid, may be in a range from 0.1 to 0.5 weight %
of a total weight of the slurry. In an example embodiment, a
content of the oxidizer, for example, periodic acid, may be in a
range from 0.25 to 0.5 weight % of a total weight of the slurry. In
an example embodiment, a content of the oxidizer, for example,
periodic acid, may be in a range from 0.5 to 1.5 weight % of a
total weight of the slurry.
[0024] In an example embodiment, the pH of the CMP slurry is from 2
to 8 and more particularly, from 3.5 to 4.5. In an example
embodiment, the pH of the CMP slurry is about 4. In another example
embodiment, the pH of the CMP slurry is about 8.
[0025] In an example embodiment, a content of the colloidal silica
is 0.5 weight % of a total weight of the slurry and a content of
the periodic acid is 0.5 weight % of a total weight of the slurry.
In an example embodiment, a content of the colloidal silica is 3
weight % of a total weight of the slurry and a content of the
periodic acid is 0.5 weight % of a total weight of the slurry.
EXAMPLE SLURRY 1
[0026] An example slurry according to the present invention
includes colloidal silica and periodic acid. The periodic acid may
act as an oxidizer of the ruthenium to form ruthenium dioxide on
the surface of the ruthenium. The content range of the periodic
acid may be from 0.1 weight % to 5 weight The content range of the
periodic acid may be from 0.5 weight % to 1.5 weight %. The content
range of the periodic acid may be from 0.1 to 5 weight The content
range of the periodic acid may be from 2.5 to 5.0 weight %. The
content range of the periodic acid may be from 0.1 to 2.0 weight %.
The content range of the periodic acid may be from 0.1 to 1.0
weight %. The content range of the periodic acid may be from 0.1 to
0.5 weight %. The content range of the periodic acid may be from
0.25 to 0.5 weight %. The content range of the periodic acid may be
from 0.5 to 1.5 weight %.
[0027] The colloidal silica may act as an abrasive. In addition to
colloidal silica, other components such as ceria, alumina, titania,
mangania, zirconia, germania or mixtures thereof can be used as an
abrasive. The content range of the abrasive may be from 0.01 weight
% to 30 weight %. The content range of the abrasive may be from
0.01 weight % to 1 weight %. The content range of the abrasive may
be from 0.01 weight % to 1 weight % to raise the removal rate of
other layers, including oxides, such as,
Plasma-Tetra-Ortho-Silicate (TEOS), tantalum oxide (TaO),
polysilicon, or silicon.
[0028] The CMP slurry may further include potassium hydroxide as a
pH controller to increase the removal rate for ruthenium and
decrease the removal rate for oxides, such as those mentioned
above. In an example, the pH range may be from 2 to 8. In another
example, the pH range may be from 3.5 to 4.5.
COMPARATIVE EXAMPLE 1
[0029] The removal rates of ruthenium, TEOS, TaO, and polysilicon
were measured as the pH of slurry was varied. In this example, the
main components were 0.5 weight % colloidal silica of 15 nm in
diameter and 0.5 weight % periodic acid. In this example, the pH
was changed by using potassium hydroxide. The results are shown in
Table 1. TABLE-US-00001 TABLE 1 R. R. of R. R. of R. R. R. R. of
ruthenium TEOS Selectivity of TaO polysilicon No. pH (.ANG./min)
(.ANG./min) (ru/TEOS) (.ANG./min) (.ANG./min) 1 1.86 363 251 1.4
>1,100 131 2 3.91 1,127 154 7.3 605 146 3 6.02 >1,300 46
>28 85 46 4 7.88 >1,300 87 >15 41 136
[0030] As shown in Table 1, the amount of potassium hydroxide may
be increased to increase the pH of the CMP slurry. In sample No. 1,
no potassium hydroxide is present. As shown in Table 1, the
selectivity between ruthenium and other materials, like TEOS, TaO
and polysilicon, may be controlled by changing the pH of the CMP
slurry.
EXAMPLE SLURRY 2
[0031] Another example slurry according to the present invention
includes colloidal silica, periodic acid, and an amine compound, as
a pH controller. The amine compound may increase the removal rate
and selectivity between ruthenium and other materials, like TEOS,
TaO, polysilicon, and silicon. The amine compound may be BHMT
(Bis-(HexaMethylene)Triamine), TMAH (TetraMethyl Ammonium
Hydroxide), TMA (TetraMethylAmine), TEA (TetraEthylAmine), HA
(Hydroxylamine), PEA (PolyEthyleneAmine), CH (Choline Hydroxide) or
choline salt. Other conditions may be the same as that of Example
Slurry 1, except using an amine compound as a pH controller.
COMPARATIVE EXAMPLE 2
[0032] The removal rates of ruthenium, TEOS, tantalum oxide (TaO)
and polysilicon were measured as the amine compound was varied. In
this example, the main components were 0.5 weight % colloidal
silica of 15 nm in diameter, 0.5 weight % periodic acid and an
amine compound that makes the pH of the slurry either 4 or 8. The
results are shown in Table 2. TABLE-US-00002 TABLE 2 Removal
Removal Removal rate rate of rate of Removal rate of Amine of
ruthenium TEOS Selectivity TaO polysilicon No. compounds pH
(.ANG./min) (.ANG./min) (ru/TEOS) (.ANG./min) (.ANG./min) 1 None
7.2 0 46 -- 124 38 2 TMAH 4 892 86 10.4 >1,200 2,314 3 TEA 4 262
148 1.8 >1,200 614 4 TEA 8 0 16 -- 22 1,308 5 TMA 4 866 144 6.0
>1,200 2,136 6 NH.sub.4OH 4 854 138 6.2 380 106 7 NH.sub.4OH 8
746 92 8.1 38 170
[0033] As shown in Table 2, the amine compound may be varied to
increase the selectivity of the CMP slurry. In sample No. 1, no
amine compound or oxidizer was present. As shown in Table 2, the
selectivity between ruthenium and other materials, for example,
TEOS, TaO and polysilicon, may be controlled by changing the amine
compound of the CMP slurry. As shown in Table 2, TMAH and TMA
exhibit better results.
COMPARATIVE EXAMPLE 3
[0034] The removal rates of ruthenium, TEOS, tantalum oxide (TaO)
and silicon were measured as the pH of slurry changed by changing
the amount of TMAH and TMA. The main components were 0.5 weight %
colloidal silica of 15 nm in diameter, 0.5 weight % periodic acid
and amine compound that makes the pH of the slurry either 4 or 8.
The results are shown in Table 3. TABLE-US-00003 TABLE 3 Removal
Removal Removal Rate Rate of Rate of Removal Rate of pH of
ruthenium TEOS Selectivity TaO silicon No. controller pH
(.ANG./min) (.ANG./min) (ru/TEOS) (.ANG./min) (.ANG./min) 1 TMAH 2
434 340 1.3 >1,100 6,102 2 3 647 134 4.8 5,872 3 4 869 116 7.5
3,036 4 5 939 408 2.3 858 5 TMA 2 485 236 2.1 744 6 3 712 128 5.6
2,328 7 4 871 120 7.3 2,246 8 5 983 188 5.2 1,852
[0035] As shown in Table 3, the removal rate of ruthenium increased
as pH increased. Moreover, Table 3 shows that not only the removal
rate of ruthenium, but also the removal rate of other layers, for
example, TaO and silicon, can be controlled by changing the pH of
the slurry.
COMPARATIVE EXAMPLE 3
[0036] The removal rates of ruthenium, TEOS, tantalum oxide (TaO)
and silicon were measured as the amount of colloidal silica was
varied. The main components were colloidal silica of 15 nm in
diameter, 0.5 weight % periodic acid and TMAH that makes the pH of
the slurry about 4. The results are shown in Table 4.
TABLE-US-00004 TABLE 4 Amount of Removal colloidal Removal Rate
Rate of Removal Rate Removal Rate silica of ruthenium TEOS
Selectivity of TaO of silicon No. (wt %) (.ANG./min) (.ANG./min)
(ru/TEOS) (.ANG./min) (.ANG./min) 1 0 46 0 -- 554 8 2 0.5 920 18
51.5 >800 400 3 1 818 20 40.9 >800 736 4 3 778 36 21.6
>800 2,050 5 5 852 64 13.3 >800 1,980 6 7 644 92 7.0 >800
2,782 7 9 722 138 5.2 >800 2,396
[0037] As shown in Table 4, the removal rate of TEOS increased,
whereas the removal rate of ruthenium was not significantly
affected as the amount of colloidal silica increased. In an example
embodiment, a suitable amount of colloidal silica may be about 3 wt
% taking the removal rate of silicon and the selectivity between
ruthenium and TEOS into consideration.
[0038] A method of forming a capacitor using ruthenium or ruthenium
alloy as a bottom electrode in accordance with an example
embodiment of the present invention is described in conjunction
with FIG. 1-7. As shown in FIG. 1, the method may include
depositing an etch stopping layer 12 and mold oxide layer 14
sequentially on a substrate 10.
[0039] As shown in FIG. 2, the method may further include defining
a trench 16 for forming a capacitor by patterning the mold oxide
layer 14. In an example embodiment, the patterning the mold oxide
layer 14 may include using at least one of a hard mask and a
photoresist. In an example embodiment, the mold oxide layer 14 may
be one of a tetraethylorthosilicate (TEOS) layer, for example, a
plasma enhanced TEOS (PE-TEOS) layer, an oxide (OX) layer, for
example, a plasma enhanced OX (PE-OX) layer, a high density plasma
(HDP) layer, an undoped silica glass (USG) layer, and a doped
phosphosilicate glass (PG) layer, for example, boron-doped
phosphosilicate glass (BPSG) layer.
[0040] As shown in FIG. 3, the method may further include forming a
space, for example, a tantalum oxide spacer 18 in the trench 16 and
depositing a ruthenium film 20 in the trench 16, but not completely
filling the trench 16, as shown in FIG. 4. In an example
embodiment, the spacer 18 may include tantalum (Ta), hafnium (Hf),
aluminium (Al), titanium (Ti), strontium titanate (Sb--Ti) of
oxides (STO), barium strontium titanate (BST) or oxides or
combinations thereof.
[0041] In an example embodiment, the ruthenium film 20 may be a
ruthenium alloy. In an example embodiment, the ruthenium film 20
may be deposited by sputtering, chemical vapor deposition (CVD), or
atomic layer deposition (ALD), all techniques commonly known in the
semiconductor processing art.
[0042] As also shown in FIG. 4, the method may further include
depositing a layer, for example, a dielectric layer, for example,
tantalum oxide 22 to completely fill the trench 16 and removing the
tops of the ruthenium film 20 and the tantalum oxide layer 22 so
that only the parts of the ruthenium film 20 and the tantalum oxide
layer 22 in the trench remain to form a separated storage node 24,
as shown in FIG. 5. In an example embodiment, the tops of the
ruthenium film 20 and the tantalum oxide layer 22 may be removed by
polishing using one or more of the slurries described above. In an
example embodiment, the polishing is CMP polishing.
[0043] In an example embodiment, the dielectric layer may include
tantalum (Ta), hafnium (Hf), aluminium (Al), titanium (Ti),
strontium titanate (Sb--Ti) or oxides (STO), barium strontium
titanate (BST) or oxides or combinations thereof.
[0044] In an example embodiment, the removal rate selectivity of
the one or more of the slurries may be greater than or equal to
5:1. In other example embodiments, the removal rate selectivity may
be greater than or equal to 20:1 or 50:1.
[0045] As shown in FIG. 6, the method may further include
completely removing the mold oxide layer 14 to form a box-shaped
bottom electrode structure and sequentially depositing a dielectric
layer 26 and a top electrode layer 28, to thereby form a complete
capacitor sequentially, as shown in FIG. 7.
[0046] Although, as shown in FIG. 7, the resulting capacitor may
have a stacked structure, the example slurries and polishing
methods in accordance with example embodiments of the present
invention may be incorporated in other methods to form capacitors
with different structures, for example, concave or OCS
structures.
[0047] Another method of forming a capacitor using ruthenium or
ruthenium alloy as a bottom electrode in accordance with an example
embodiment of the present invention is described in conjunction
with FIGS. 8-17. As shown in FIG. 8, a first interlayer dielectric
film 20 may be formed on a semiconductor substrate 10, and a
contact 22 may be connected to an active region of the
semiconductor substrate 10 through the first interlayer dielectric
film 20. In an example embodiment, the contact 22 may include a
polysilicon layer 22a contacting the active region of the
semiconductor substrate 10 and a contact plug 22b deposited on the
polysilicon layer 22a and exposed on the first interlayer
dielectric film 20. The contact plug 22b may serve as a barrier for
reducing or preventing an undesired reaction from occurring between
a lower electrode material and the polysilicon layer 22a in a
subsequent thermal treatment process. The contact plug 22b may be
formed of only the TiN layer, or can be formed of TiAlN, TiSiN,
TaN, TaSiN, or TaAlN.
[0048] As shown in FIG. 9, a second interlayer dielectric film 38
comprising an etch stop layer 32, an oxide layer 34, and an
anti-reflection layer 36 may be formed on the resultant structure
on which the contact 22 is formed. In order to form the second
interlayer dielectric layer 38, first, the etch stop layer 32,
e.g., an SiN layer, may be formed to a thickness of about 50 to 100
.ANG. on the upper surface of the first interlayer dielectric film
20 and an upper surface of the contact plug 22b which is the
exposed surface of the contact 22. The oxide layer 34 having a
thickness corresponding to a desired lower electrode height may be
formed on the etch stop layer 32. The oxide layer 34 can be formed
of any oxide that is typically used to form an interlayer
dielectric film. An anti-reflection layer 36 made of SiON may be
formed on the oxide layer 34. In an example, embodiment, a
photoresist pattern 40 may be formed on the second interlayer
dielectric film 38.
[0049] As shown in FIG. 10, the second interlayer dielectric film
38 may be etched up to the etch stop layer 32 which acts as an etch
end point using the photoresist pattern 40 as an etch mask. As a
result, a concave pattern 38a may be formed. A portion formed on
the contact 22 among the etch stop layer 32 used as the etch end
point may be completely removed by over etching. As a result, the
concave pattern 38a may include an etch stop layer pattern 32a, an
oxide layer pattern 34a and an anti-reflection layer pattern 36a,
and a storage node hole 38h exposing the upper surface of the
contact 22. Thereafter, the photoresist pattern 40 may be
removed.
[0050] FIGS. 11 and 12 are cross-sectional views illustrating the
formation of an adhesion spacer 50a for improving the bonding
between the concave pattern 38a and a lower electrode formed in a
subsequent process, on the sidewalls of the concave pattern 38a
exposed by the storage node hole 38h, in accordance with an example
embodiment of the present invention.
[0051] In more detail, in FIG. 11, an adhesion layer 50 may be
formed to cover the contact 22 exposed by the storage node hole
38h, and the sidewall and upper surface of the concave pattern 38a.
The adhesion layer 50 can be formed of at least one material
selected from the group consisting of Ti, TiN, TiSiN, TiAlN,
TiO.sub.2, Ta, Ta.sub.2O.sub.5, TaN, TaAlN, TaSiN, Al.sub.2O.sub.3,
W, WN, Co, and CoSi, using a chemical vapor deposition (CVD)
method, a physical vapor deposition (PVD) method, a metal-organic
deposition (MOD) method, a sol-gel method, or an atomic layer
deposition (ALD) method.
[0052] In accordance with an example embodiment of the present
invention, the adhesion layer 50 may undergo an etchback process
until the adhesion spacer 50a remains on only the sidewall of the
concave pattern 38a. Thus, only the adhesion spacer 50a and the
contact 22 are exposed within the storage node hole 38h.
[0053] FIGS. 13-16 are cross-sectional views illustrating the
formation of a lower electrode 60a in the storage node hole 38h, in
accordance with an example embodiment of the present invention.
[0054] As shown in FIG. 13, a first conductive layer 60 may be
formed to cover the upper surface of the contact 22 and the
adhesion spacer 50a which are exposed within the storage node hole
38h, and the upper surface of the concave pattern 38a.
[0055] The first conductive layer 60 can be formed by depositing a
platinum-group metal, a platinum-group metal oxide, or a material
having a perovskite structure using a PVD or CVD method. For
example, the first conductive layer 60 can be formed of Pt, Ru, Ir,
RuO.sub.2, IrO.sub.2, SrRuO.sub.3, BaSrRuO.sub.3, or CaSrRuO.
[0056] In an example embodiment, as shown in FIG. 14, a sacrificial
layer 62 having a thickness which can sufficiently fill the storage
node hole 38h may be formed on the resultant structure on which the
first conductive layer 60 has been formed. The sacrificial layer 62
can be a photoresist layer or an oxide layer.
[0057] The first conductive layer 60 and sacrificial layer 62 on
the concave pattern 38a may be etched back or removed by chemical
mechanical polishing (CMP) until the upper surface of the concave
pattern 38a is exposed. Consequently, the first conductive layer 60
may be divided into a plurality of lower electrodes 60a as shown in
FIG. 15. Each of the lower electrodes 60a may cover the upper
surface of the contact 22, and the adhesion spacer 50a in the
storage node hole 38h.
[0058] In the storage node hole 38h, the residual portion 62a of
the sacrificial layer 62 may remain on the lower electrode 60a. The
residual portion 62a of the sacrificial layer 62 may be removed by
ashing or wet etch, thus obtaining a resultant structure as shown
in FIG. 16. In an example embodiment, when the sacrificial layer 62
is a photoresist layer, the residual portion 62a of the sacrificial
layer 62 may be removed by ashing. In an example embodiment, when
the sacrificial layer 62 is an oxide layer, the residual portion
62a of the sacrificial layer 62 may be wet-etched out.
[0059] In an example embodiment, the photoresist layer or oxide
layer forming the sacrificial layer 62 can be removed at an
excellent selectivity with respect to SiON forming the
anti-reflection layer pattern 36a in the upper portion of the
concave pattern 38a and a conductive material forming the lower
electrode 60a. Therefore, when the residual portion 62a of the
sacrificial layer 62 is removed, other portions on the
semiconductor substrate 10 are not damaged.
[0060] Referring to FIG. 17, a dielectric layer 70 may be formed on
the lower electrode 60a. The dielectric layer 70 may be formed of
at least one material selected from the group consisting of
Ta.sub.2O.sub.5, Al.sub.2O.sub.3, SiO.sub.2, SrTiO.sub.3,
BaTiO.sub.3, (Ba,Sr)TiO.sub.3, PbTiO.sub.3, (Pb,Zr)TiO.sub.3,
Pb(La,Zr)TiO.sub.3, Sr.sub.2Bi.sub.2NbO.sub.9, Sr.sub.2Bi.sub.2
TaO.sub.9, LiNbO.sub.3, and Pb(Mg,Nb)O.sub.3. In an example
embodiment, the dielectric layer 70 may be formed by the PVD
method, the CVD method, or the sol-gel method.
[0061] In an example embodiment, a second conductive layer 80 may
be formed on the dielectric layer 70, thus forming an upper
electrode of a capacitor. The second conductive layer 80 may be
formed by depositing a platinum-group metal, a platinum-group metal
oxide, TiN, or a material having a perovskite structure using the
PVD method, the CVD method, the MOD method, or the ALD method. For
example, the second conductive layer 80 can be formed of Pt, Ru,
Ir, RuO.sub.2, IrO.sub.2, TiN, SrRuO.sub.3, BaSrRuO.sub.3, or
CaSrRuO.sub.3.
[0062] FIG. 18 illustrates a storage electrode 142 formed in a One
Cylinder Stack (OCS) structure, in accordance with an example
embodiment of the present invention. As shown in FIG. 18, an OCS
capacitor may include a bit line 122 and a first capping layer 124
on an integrated circuit substrate 100.
[0063] In an example embodiment, the first capping layer 124 may
cover the bit line 122. The bit line 122 may be formed as a first
conductive layer connected to an active region of the semiconductor
substrate 100 through interlayer dielectric films 110 and 120 on
the substrate 100 on which cell array devices 102, for example,
cell array transistors are formed. A first insulating layer may be
formed on the entire surface of the resultant structure using a
first insulating material such as Si.sub.3N.sub.4. The first
insulating material may be anisotropically etched to form first
capping layer 124.
[0064] In an example embodiment, an OCS capacitor may further
include a first interlayer dielectric film 130 and a second capping
layer 134. The first interlayer dielectric film 130 may be formed
by forming an insulating film such as an oxide film by chemical
vapor deposition (CVD) on the entire surface of the resultant
structure using a second insulating material having an etch rate
different from that of the first insulating material. The first
interlayer dielectric film 130 may be planarized by a chemical
mechanical polishing (CMP) process with the first capping layer 124
acting as an etch stop layer. The second capping layer 134 may be
formed by forming a second insulating layer on the entire surface
of the resultant structure using a third insulating material, for
example, Si.sub.3N.sub.4. As shown in FIG. 18, the second capping
layer 134 may be planar.
[0065] In an example embodiment, an OCS capacitor may further
include a plug e1 for forming the storage contact of the cell array
region and forming wiring layers e2, e3 and e4 of the peripheral
circuit region. In an example embodiment, a second conductive layer
may be formed by depositing a metal having excellent filling
properties, for example, tungsten (W) or TiN, using CVD.
[0066] In an example embodiment, an OCS capacitor may further
include a second interlayer dielectric film 140 only in the
peripheral circuit region. The second interlayer dielectric film
140 may be formed by forming an insulating film such as an oxide
film on the entire surface of the resultant structure and removing
the insulating film by etching the insulating film in the cell
array region using the second capping layer 134 as an etch stop
layer.
[0067] In an example embodiment, an OCS capacitor may further
include a storage electrode 142 formed to electrically connect to
the active region of the substrate 100 through the plug e1 by
forming a conductive layer such as a doped polysilicon layer in the
cell array region and patterning the conductive layer. It is also
possible to form a storage electrode having a structure in which a
TiN film and a polysilicon layer are stacked by forming the TiN
film and the polysilicon layer and patterning the TiN film and
polysilicon layer.
[0068] As shown in FIG. 18, an OCS capacitor may include a
dielectric film 144, of a dielectric material such as
Ta.sub.2O.sub.5 and (Ba, Sr)TiO.sub.3, on the surface of the
storage electrode 142 in a cell array region and a plate electrode
146 on the dielectric film 144.
[0069] Although example embodiments of the present invention are
directed to slurries, polishing methods using the slurries, and
method of forming a surface of a capacitor using the slurries,
other etching materials may also be used, either in place of, or in
addition to the slurries described herein, including, but not
limited to etchants that includes a mixture of NH.sub.4F and HF
(commonly referred to in the semiconductor processing art as "LaI
solutions") and mixtures of NH.sub.3, H.sub.2O.sub.2 and deionized
water (commonly referred to in the semiconductor processing art as
an "sc1 solution").
[0070] Although example embodiments of the present invention are
directed to polishing ruthenium films, other films, for example,
Pt, Ir, RuO.sub.2, IrO.sub.2, SrRuO.sub.3, BaSrRuO.sub.3, or
CaSrRuO, may also be polished.
[0071] Although example embodiments of the present invention are
directed to slurries, slurries with particular classes of
components (abrasive, oxidizer, and/or pH controller, etc.),
slurries with particular pHs (4, 8, etc), slurries with particular
components (colloidal silica, periodic acid, BHMT, etc.), slurries
with particular weight percentage ranges of components, slurries
with particular weight percentages of components, polishing methods
using the slurries, and methods of forming a surface of a capacitor
using the slurries, each of the above features may be mixed,
matched, and/or interchanged with other features to create
numerous, other example embodiments of the present invention.
[0072] It will be apparent to those skilled in the art that other
changes and modifications may be made in the above-described
example embodiments without departing from the scope of the
invention herein, and it is intended that all matter contained in
the above description shall be interpreted in an illustrative and
not a limiting sense.
* * * * *